Updated People Search docs

Updated copy and text to reflect new property choices in People Search:

* contains (property value must contain what is submitted i.e. SPRING
would work for SPRING2014 and SPRINGCOUPON)
* equals (property value must match exactly what is submitted i.e
SPRING would look for exactly SPRING)
* empty (property value exists, but is empty or nulll; this is used to
check for any data sets that may be missing data or that should contain
something)
* any (all users who have the property, including empty values)
Merge pull request #81 from chuckjliu/gh-pages

Updated People Search docs